Range finder



Oct 9 1945' E. K. KAPRELIAN 2,386,614

RANGE FINDER Filed July 1l, 1944 EE? J Edward Eigenheiten,

Appiicaticn italy lll, il@

lllifiis invention relates to a combined View rangender and to anoptical system whereby the rangeiinder image is enlarged with respect tothe viewfinder image.

In all combined view and range inders such as are used .with miniaturecameras the scene to be photographed is seen in reduced size through aninverted Galilean system, the virtual image formed by the front negativelens being brought to a comfortable viewing distance by the positiveeyepiece lens. The indirect beam is usually brought into the center ofthe viewfinder ileld by means of a reflecting mirror and asemitransparent mirror fixed at a 45 angle between the elements of theGalilean system. In such systems of the prior art both the viewnderimage and the rangeflnder image are reduced by about one half. As aresult the optical base of the rangender is about half the mechanicalbase and the accuracy of focusing is reduced proportionately.

It is an object of this invention to provide means whereby part of therangelnder image is enlarged to unit magnification or larger.

It is a further object of this invention to provide means forintroducing or removing the image enlarging means at will, therebypermitting the view and rangender system to operate either as a normalsystem or as a magnifying system.

Other objects and advantages of the invention will become apparent fromthe following description when read in connection with the accom-lpanying drawing in which:

Fig. 1 shows a view and range nder system' l according to the invention.

Fig. 2 shows the appearance of a subject as viewed through the view andrangeflnder systemV described.

Fig. 3 shows a'modification of the system in Fig. 1 in which a pair ofcemented prisms are employed.

Fig. 4 shows a further modication of the optical arrangement of therangender.

Fig. 5 shows a still further modication of the system.

Fig. lshows a viewnder portion consisting of an inverted Galilean systemincluding a negative front element I and a positive eyepiece 2. Lightfrom the subject enters the finder system as at A, and also enters adeilecting mirror 3 as at A'.

Light striking mirror 3 is deflected through a. negative lens Il to asemi transparent mirror l where rays A and A combine and enter eye-`piece 2. Lenses-l and ll are of the same power and are locatedequdistantly from' mirror I as in the usual rangender of this type. Acam surface i@ carried by the camera lens, not shown, presses against aroller carried by arm 9 which in turn moves mirror t carried on arm S.

Interposed between negative ienses i and il and mirror 6i arev positivelenses 5 and Si respecftively, These lenses are smali in diameter ascompared to lenses l and il and comprlsethe objective lenses ci asupplementary, internal Galilean system.. Lens il comprises the eyepieceof this system. Some of the light rays enteringy lenses l and il willpass through lenses 5 and 6 and will pass through lens l and througheye= piece vl.. Thus, the central portion of the range-J iinder imagewill be magnied. The lenses E, G and l of the internal Galilean systemmay be of such power as to result in. unit magnification at the centerof the eld or may be altered to yield a unal magnification greater orless than unity.

Figure 2 shows the appearance of a subject within the field oi view ofthe rangender which is the subject of this invention. The scene to bephotographed falls within the larger rectangle while therangeinder imageappears smaller rectangle, as in the usual combined rangefinder andviewnder. Part of the rangefinder image is enlarged by the internalfalilean system 'as is shown within the circle. though some of the ileldis lost due to the magnification of the internal Galilean system aslight shifting of the eye behind the eyepiece lens will permit the eyeto see around the rear (negative) lens of the internal Galilean systemand to thereby see all parts of the scene to be photographed. Also,

. as explained below regarding Fig. 5 the internal Galilean system maybe pivoted or dropped out of the way when desired.

Figure 3 shows a modification in which a pair of cemented prisms areplaced within the inverted Galilean finder system having a. negativefront lens 3l and a positive eyepiece 32. Light from the subject as atA' enters deviatingmirror 33 supported on arm 38 and is diverted throughnegative lens 3B and into a 45 prism lll where it strikes a semireflecting surface 3l.' and is directed into eyepiece 32, joining rey Awhich has passed through lens 3l, and prismsl I! and Il. Lenses 3l and30 are of equal power and are spaced equidistantly from surface 3E. Partof the light entering lens 3l passes through positive lens V35 and partof the light entering lens 3l passes through positive lens 38, lenses I5and 3l Comprising the objectives of an internal Galilean system of which31' constitutes theeyepiece. In operation the modication of Fig. 3 isidentical thin theV to Fig. 1, the main advantage residing in the factthat the prisms provide convenient, accurate supsome of this lightentering a small internal- Gali'lean system comprising lenses l5 and d5placed between the mirror ad and eyepiece d2. In this modification,although the internal Galilean system has not been divided and placedbefore and behind the semi-transparent mirror, the opticalcharacteristics remain the same. Lens d6 may be cemented to eyepiece l2for convenience. Lens 45 may be cemented to a sheet of glass ortransparent plastic for support.

The modification of Fig. is similar to Fig. 4 in that lenses 5i, 53 and52 and mirror 5e are identical to the corresponding elements in Fig. 4.The Galilean system --i of Fig. 4 is replaced in this modication bymember 5'? which may be made of glass or of any well known transparentplastic material of suitable optical characteristics. Member 5l' carriesa collective surface 55 facing the mirror 5d and a relatively deepnegative surface 56 facing eyepiece 52. Member 5l may be swung out ofposition and out of the eld of view when desired by any convenientmechanical linkage connected to arm 58. Preferably the arrangementshould be such that when pressure such as the users finger is applied tothe focusing knob or wheel. member 57 will be moved into the positionshown in Figure 5. The magnifying effect of member 5l then aids inobtaining sharp focus. When the users linger is removed from theYfocusing knob member 5l is returned to its inoperative position bygravity or preferably by a spring.

What I claim as my invention is: i. InV a combined view finder and rangefinder 'of the coincidence type, a partially reflecting ray dividingsurface, an inverted Galilean view finder system having its negativeelement situated before the ray dividing surface and its positiveelement behind said surface, a movable mirror displaced from the viewfinder system and forming with said system the base for the range nder,a negative lens having the same power and spacing from said ray dividingsurface as said view -nder negative lens and located between saidmovable mirror and said ray dividing surface and acting to diverge lightdirected by the mirror to said ray dividing means, and an afocalmagnifying system of the positive Galilean type comprising at least onepositive and one negative lens enclosed within the range finder systemto magnify corresponding parts of the central portions of the rangefinder images.

2. A combined View finder and range finder as claimed in claim l inwhich the afocal magnifying system comprises a positive lens placedbehind the negative element of the inverted Galilean view finder, apositive lens placed behind said negative lens which cooperates with themovable mirror and a negative lens placed before the positive element ofthe inverted Galilean view finder system.

3. A combined view finder and range finder as claimed in claim 1, saidray dividing surface being formed at the diagonal surface of a pair of45 prisms, the lenses of the afocal magnifying system being attached tothe faces of the prisms.

y 4. A combined view nder and range nder as claimed in claim 1 in whichthe afocal magnifying system comprises a solid pencil of refractivematerial having a positive front surface and a. negative rear surfaceand located between the ray dividing surface and the positive eyepieceof the inverted Galilean view finder eyepiece.

5. A combined view nder and range nder as claimed in claim 1 in whichthe afocal magnifying system comprises a solid pencil of refractivematerial having a positive front surface and a negative rear surface andlocated between the ray dividing surface and the positive eyepiece ofthe inverted afocal magnifying view finder eyepiece, said Galileanpencil being movable into and out of the field of view of the view ndersystem.

6. In a combined view finder and range nder of the coincidence type, apartially reecting ray dividing surface, an inverted Galilean view ndersystem having its negative element situated before the ray dividingsurface and its positive element behind said surface whereby directbeams from an object pass through the negative lens and mirror andthrough the positive lens, a movable mirror displaced from the viewfinder systern and forming therewith the base for the range finder, saidmovable mirror directing deviated beams from an object toward saidpartially reflecting ray dividing surface where said direct and deviatedbeams combine, a negative lens between said movable mirror and said raydividing surface, said negative lens being equal in power and smaller insize than the negative element of said inverted Galilean view findersystem and being spaced from said ray dividing surface equidistantlywith the negative element of said inverted Galilean view findersystem,-and afocal magnifying means of the Galilean type enclosed withinthe range finder system whereby corresponding portions of the imagesformed by the direct and deviated beams of the range nder are magnied,the lenses of said afocal magnifying system being smaller than thelenses of the view nder and range finder, whereby only a portion of theview nder field is magnified.

7. In a combined view finder and range finder of the coincidence type, apartially reecting ray dividing surface, an inverted Galilean view ndersystem having its negative element situated before the ray dividingsurface and itsI positive element behind said surface whereby directbeams from an object pass through the negative lens and mirror andthrough the positive lens, a movable mirror displaced from the view ndersystem and forming therewith the base for the range finder, said movablemirror directing deviated beams from an object toward said partiallyreecting ray dividing surface where said direct and deviated beamscombine,l a negative lens between said movable mirror and said raydividing surface, said negative lens being equal in power and smaller insize than the negative element of said inverted Galilean view findersystem and being spaced from said ray dividing surface equidistantlywtih the negative element of said inverted Galilean `viewfinder systemand an afocal magnifyng system of the Galilean type enclosed within therange finder system through which both the direct and deviated beamspass whereby both images of the range iinder are magnified, the lensesof said magnifying s'ystem being smaller than those of said View finderwhereby the range finder images cover a smaller angular field than saidviewnder images.

8. In a combined View finder and range finder of the coincidence type, apartially reiiecting ray dividing surface, an inverted Galilean Viewlnder system having its negative element located before the ray dividingsurface and its positive element behind said surface, a movable mirrordisplaced from the viewlinder system and forming with said system thebase for the rangender, a negative lens located between said mirror andsaid ray dividing surface and having the same power and separation fromsaid ray dividing surface as said viewfinder negative lens and an afocalmagnifying system centered with respect to the rangender system andacting to magnify corresponding portions of the images formed by therangeiinder, the lenses of said magnifying system being smaller than theelements of the rangeflnder whereby onlytne central portion of the iieldseen through the rangender is magnied.

9. In a combined viewiinder and rangeflnder of the coincidence typehaving a partially reiieeting ray dividing surface, an inverted Galileanviewfinder system having its negative lens in front of and its positivelens in back of said ray dividing surface, a movable mirror displacedfrom the viewlinder system and forming with said system the base for therangeiinder and a negative lens located between said mirror and said raydividing surface and having the same power and separation from said raydividing surface as said viewfinder negative lens, magnifying means forenlarging a portion of the rangeiinder iield comprising an afocalmagnifying system of the Galilean type placed in axial alignment withinthe rangeflndersystem and having lenses smaller in size than therangefinder elements.

EDWARD K. KAPRELIAN.

